Proposed is a miniature sensor for real-time measurement of nano-particle size, concentration, surface area and lung deposition metrics. This instrument combines two novel technologies: (1) a self- sustaining laminar-flow water condensation particle counter and collector developed by our firm and (2) the opposed migration aerosol classifier developed at the California Institute of Technology. The self- sustaining water condensation counter provides single particle detection, does not require liquid fill reservoirs, and can be operated in any orientation. The opposed migration aerosol classifier provides particle size-selection based on electrical mobility in an inherently compact form. Both technologies are compatible with devices small enough to be wearable. The instrument is configured to cover the particle size range from 10 nm to 200 nm when configured as a personal sampler, and can extend to near 1 um when configured as a hand-held device. Reported parameters are nano-particle number distribution, total number concentration, geometric mean diameter, and region-specific respiratory deposition potential. In Phase I research we demonstrated the precision and accuracy of our technology. In Phase II we will design, construct and test an integrated system that we will be unobtrusive, battery operable and suitable for personal monitoring. This instrument will provide a means to monitor, on a routine basis, human exposures associated with airborne synthesized nano-materials.